1. Field of Invention
The present invention relates to optical/electronic sorting of agricultural products.
2. Description of Prior Art
In U.S. Pat. No. 3,012,666 a technique of electronic color sorting of agricultural products was disclosed. Color masks defining limits between acceptable and unacceptable colors for the product as a relative mixture of two component colors were electronically formed. Agricultural products were optically scanned to measure the relative presence of these component colors, and the measurements taken were compared with the limits defined by the color masks. Products with colors found unacceptable were then separated.
As pointed out in U.S. Pat. No. 3,899,415, in actual use sorters using the foregoing color sorting technique in service often encountered several factors which would cause the limit settings to fluctuate. To compensate for this, an adjustment, known as normalization, of the electronic settings for acceptable color was periodically made with a normalizing cicuit. According to this patent, however, a separate normalizing circuit for component color and for each optical sensor was needed. This significantly increased the number of electronic components in the sorter. Since these types of sorters often were required to perform in remote areas of underdeveloped nations and under harsh service conditions, reliability of the sorter and maintenance and the availability of replacement parts were frequently encountered problems.
Further, it was necessary to insure that the color component signals being processed at any particular time came in actuality from the same scanned portion of the product, requiring synchronization of the receipt and processing for each of the component color signals received from the optical scanning portion of the apparatus. Again, harsh service conditions often in remote locales made this a substantial problem.
U.S. Pat. Nos. 3,066,797 and 3,993,899 used light conducting members as fiber optic bundles in sorters of this type. The bundles of fiber optic material were divided into groups of bundles, one for each component color, and each group passed through a different color filter to a photocell to separate for processing the color components of the object being scanned. Physical division of the fiber optics into bundles, however, accentuated the framing problems. Each optical fiber in effect faced one portion of the surface of the object being scanned. When this fiber was separated into one of the color groups, however, only that color component of that surface area of the product was available for processing and comparison. The use of small diameter optic fibers was mentioned, but this increased the cost of the sorter. Another possibility discussed was random distribution of the fibers for the different colors within the bundle.